The present invention generally relates to a multilayer reflective polymeric body or film which, when illuminated by means of a back light source, transmits such light. The invention also relates to articles produced therefrom which include decorative trim, lighting lenses for automotive, commercial and residential lighting applications, and structural parts such as refrigerator doors, and the like. The present invention also relates to a method by which such articles can be produced from the multilayer reflective polymeric body or film without causing undesirable iridescent colors.
By way of example, in the automotive industry, automobile stylists and designers are always seeking ways in which a particular vehicle's appearance can be differentiated. Most recently, automobiles have been approaching very similar designs in view of the rather limited number of ways in which automobiles bodies can be aerodynamic as well as fuel efficient. Consequently, stylists and designers are faced with the formidable task of differentiating such vehicles.
To the extent that vehicle headlights, taillights and the like are required for functional purposes, designs of the vehicle adjacent to areas where lights are needed have been limited since the associated lighting lenses disrupt the styling contours on the vehicle and exhibit color mismatches. Thus, it is desirable to be able to render vehicle lights indiscernible by blending the vehicle body lines, colors, and/or decorative trim with a reflective and/or colored surface which conceals the lighting, and yet conforms to standard lighting requirements when the lights are illuminated.
Such a design option would also find utility in a wide variety of other areas in addition to the automotive industry. For example, in the area of consumer appliances, the housings on such appliances could be made to exhibit one color or appearance when viewed and yet permit internal items to become visible when illuminated. For example, a refrigerator door or portion thereof could be reflective and/or colored to match, blend, or contrast with the reminder of the appliance and yet become transparent when illuminated by a light inside the refrigerator so as to expose its contents to view without opening the door.
Additionally, in the areas of commercial and residential lighting, it would be desirable to be able to provide lights which would blend in with the chosen decor, and yet illuminate a room when turned on. This would expand on the variety of options available for interior decoration and the styles of lamps and lighting. For example, in restaurants, nightclubs and the like, hand rails, floor tiles, panels, etc., it would be desirable to have such items reflective in appearance yet appear differently when back lit.
Conventional methods for fabricating reflective surfaces include forming such surfaces of highly polished metals. Such polished metal surfaces are useful to reflect light but such surfaces are opaque and they cannot be used to hide lamps or other lighting from view. Because of the high costs, weight, environmental concerns, and fabricating problems involved in using metals, there has been a shift to use plastic surfaces which contain thin coatings of metal thereon.
Thus, metal coated plastic articles are now commonly found as both decorative and functional items in a number of industries. Such articles are used as bright work for consumer appliances such as refrigerators, dishwashers, washers, dryers, radios, and the like. These types of articles are also used by the automotive industry as head lamp reflectors, bezels, radio knobs, automotive trim, and the like. Again, however, such reflective surfaces are designed to be substantially opaque and cannot be used to conceal lamps or other lighting from view.
There have been a wide multitude of lighting designs in several areas such as the automobile industry. For example, Goldbaum et al, U.S. Pat. No. 3,321,618 disclose an automotive vehicle lamp assembly with a snap-in lens and Kirsch, U.S. Pat. No. 4,020,338 discloses an automobile lighting lens which provides an adaptor for styling headlights. Further, Egawa et al, U.S. Pat. No. 5,005,949, discloses an anti-glare covering for illuminated lights which substantially reduces perceived glare from lighting. However, none of these attempts in the art provide a lighting lens or covering which possesses the desired feature of reflectivity and yet transmissivity upon exposure to a back light source.
Multilayer articles of polymers are known, as are methods and apparatus for making such articles. For example, such multilayered articles may be prepared utilizing multilayer coextrusion devices as described in commonly-assigned U.S. Pat. Nos. 3,773,882 and 3,884,606 to Schrenk. Such devices are capable of simultaneously extruding diverse thermoplastic polymeric materials in substantially uniform layer thicknesses. The number of layers may be multiplied by the use of a device as described in commonly-assigned U.S. Pat. No. 3,759,647 to Schrenk et al.
Alfrey, Jr. et al, U.S. Pat. No. 3,711,176, teach a multilayered highly reflective thermoplastic body fabricated using thin film techniques. That is, the reflective thin film layers of Alfrey, Jr. et al relied on the constructive interference of light to produce reflected visible, ultraviolet, or infrared portions of the electromagnetic spectrum. Such reflective thin films have found use in decorative items because of the iridescent reflective qualities of the film. See also, Cooper, U.S. Pat. No. Re. 31,780.
However, the films of Alfrey, Jr. et al are extremely sensitive to thickness changes, and it is characteristic of such films to exhibit streaks and spots of nonuniform color. Further, color reflected by such films is dependent on the angle of incidence of light impinging on the film. Thus, such films are not practical for uses which require uniformity of reflectivity. Moreover, such films are not practical to thermoform into articles since localized thinning of the layers during thermoforming causes alterations in the reflective characteristics of the films.
More recently, reflective multilayer polymeric films and sheets formed of optically thick layers (optical thickness of greater than about 0.45 .mu.m), a combination of optically thick and optically very thin layers (optical thickness of less than about 0.09 .mu.m), or combinations of optically thick, optically thin, and optically very thin layers have been taught which exhibit a substantially colorless uniform silvery reflective appearance. See, Wheatley etal, U.S. Pat. No. 5,122,905; Wheatley, U.S. Pat. No. 5,122,906; and Wheatley etal, U.S. Pat. No. 5,126,880. Wheatley et al teach using these reflective films and sheets for many of the same uses as polished metal and metallized plastic sheets have been heretofore used.
Accordingly, the need still exists in this art for a polymeric body or film which is reflective, and yet is capable of transmitting light upon exposure to a back light source for a variety of applications including automotive, commercial, and residential applications. There is also a need for a method of forming such a polymeric body or film into a variety of useful shapes.